The damage behavior of a sort of high strength titanium alloy target was studied by armor piercing test. The characteristics and the mechanism of damaging were analyzed according to damage appearance of the armor plate. Results show that at the opening stage, the bullet head enters more easily the target board, and metal accumulation is found on the target plate surface, but there is no overheated metal melting phenomenon. The adiabatic shear band is found at the stable stage. The large non-homogeneous deformation in adiabatic shear bands causes microcracks and micropores. The cracks initiate and propagate along adiabatic shear bands and these large cracks result in falling of fragments from the surface of penetrated hole. As a result, the armor plate is deteriorated.